BIOTREATMENT TECHNOLOGIES FOR EXPLOSIVES-CONTAMINATED SOILS
|M.L. Hampton and W.E. Sisk, U.S. Army Environmental Center, Aberdeen Proving Ground, Maryland 21010-5401||
Although uncertainties exist with efforts to quantify the problem, energetics have been determined to be the largest environmental cleanup challenge at Army sites. Depending on the concentrations present, these explosives-contaminated soils can pose both a reactivity and toxicity hazard. Treatment of the contaminated soils is necessary to prevent the migration of hazardous substances and the potential for ground water contamination. While incineration is the current proven treatment technology, its capital and operating costs are high, and public acceptance has diminished.
Bioremediation technologies are currently being developed by the U.S. Army Environmental Center (USAEC) as alternatives to incineration. The application of landfarming to treating explosives-contaminated soils gained early interest due to its success in treating other organic wastes: petroleum hydrocarbons, pentachlorophenols, and polycyclic aromatic hydrocarbons. The potential for landfarming has not been realized. A 1991 pilot-scale study of landfarming explosives-contaminated soils in California failed to achieve the target cleanup levels.
Fungal degradation of explosives has been shown to be successful in repeated laboratory studies involving pure cultures of white rot fungus. However, subsequent pilot-scale demonstrations had difficulties overcoming competition from native bacterial populations, toxicity inhibition, chemical sorption, and the inability to meet treatment levels.
In 1992, USAEC demonstrated the effectiveness of windrow composting of explosives-contaminated soils. Composting is currently being employed as the remedial action in a Superfund site at Umatilla Depot Activity, OR, and is being considered for other sites.
Slurry phase biotreatment, in which contaminated soils are biodegraded in an aqueous suspension, was successfully demonstrated at Joliet Army Ammunition Plant, IL, in 1995. This system, which uses a native microbial consortium molasses as a co-substrate, and alternating electron acceptor conditions, consistently achieved TNT removal rates above 99%. In addition, pilot tests of a proprietary anaerobic bioslurry process have generated interest among researchers in its promise of degradation along a different metabolic pathway.
The presentation will compare the results of tests of these processes, and their relative advantages. This review will address the Army perspective on these biotreatment techniques, including the challenge to develop engineering and cost data to make these technologies fieldable. This is becoming increasingly important, as remediation schedules at many explosives sites call for cleanup to begin in the next few years.
Key words: explosives-contaminated soil, bioremediation, fungal degradation, windrow composting, slurry phase biotreatment
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